(1) Field of the Invention
The present invention relates to a semiconductor integrated circuit (IC) device, more particularly to a test circuit for an IC device which contains a variety of semiconductor integrated circuits in a chip thereof.
(2) Description of the Prior Art
IC's are usually mass produced for reasons of reduction of unit costs and standardization of capabilities. The economic considerations, etc. make it advantageous to mass produce IC's having a main-semiconductor circuit and a sub-semiconductor circuit as an option at one time. The mass produced optional semiconductor circuits of each IC chip are then selectively made active by prepackaging wire bonding in accordance with individual user needs.
For example, a dynamic metal insulated semiconductor (MIS) memory circuit is generally used together with a socalled refresh counter. The aforesaid main-semiconductor circuit may be used for the dynamic MIS memory circuit, and the aforesaid sub-semiconductor circuit may be used for the refresh counter. Many users, however, may not need the latter circuit. In such cases, the sub-semiconductor circuit is offered as an option. If a user does not need the optional circuit, wire bonding is not effected in the IC manufacturing process.
After packaging, the IC products are usually tested to confirm whether they contain both active main and subsemiconductor circuits or only active main-semiconductor circuits. The IC packages are then labeled according to the results of the tests.
In the confirmation test of the prior art, a predetermined test signal is externally supplied to the IC package under testing to cause the IC to perform an operation based on the signal. If the results of the test confirm the operation of a first function, it is concluded that the IC product has only an active main-semiconductor circuit. However, the results confirm the operation of a second function, it is concluded that the IC product has both active main and sub-semiconductor circuits.
In the prior art, however, whether the IC product includes only a main-semiconductor circuit or both a main-semiconductor circuit, and active sub-semiconductor circuit depends on whether the sub-semiconductor circuit is commonly connected to a pin leading to an external power source. In activating the sub-semiconductor circuit, it is also necessary to connect its input ports to the specified pins of the IC package.
Therefore, in the prior art test, if it is desired to confirm the operation of the second function in the IC, but only the first function operated, there is no way to determine whether both or only one of the wire bondings for connection with the external power source and the input ports are faulty. This is inconvenient in view of IC production management.